assume cs:code

code segment

    mov ax, 1000H

    mov ds, ax

    mov al, 4

    mov ds:[0], al

    add al, 1

    mov ds:[1], al
    
    add al, 1
    
    mov ds:[2], al ; 往数据段寄存器添加数据
    
    mov bx, 0

    mov ax, ds:[bx]

    add bx, 1

    mov ax, 4c00H   ; sf  
    int 21H

code ends

end